4547ca52d2
This reverts commit 7e4b109315.
With no new overflows reported, revert debugging code and stop
storing shadow stack base addresses in memory.
Bug: 120045415
Change-Id: I9aeb946073999e52f2087075e79a8854cfff1732
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
144 lines
2.4 KiB
C
144 lines
2.4 KiB
C
/*
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* Shadow Call Stack support.
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*
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* Copyright (C) 2018 Google LLC
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*/
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#include <linux/cpuhotplug.h>
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#include <linux/mm.h>
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#include <linux/mmzone.h>
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#include <linux/slab.h>
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#include <linux/scs.h>
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#include <linux/vmstat.h>
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#include <asm/scs.h>
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#define SCS_END_MAGIC 0xaf0194819b1635f6UL
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static inline void *__scs_base(struct task_struct *tsk)
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{
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return (void *)((uintptr_t)task_scs(tsk) & ~(SCS_SIZE - 1));
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}
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static inline void *scs_alloc(int node)
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{
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return kmalloc(SCS_SIZE, SCS_GFP);
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}
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static inline void scs_free(void *s)
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{
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kfree(s);
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}
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static struct page *__scs_page(struct task_struct *tsk)
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{
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return virt_to_page(__scs_base(tsk));
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}
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static inline unsigned long *scs_magic(struct task_struct *tsk)
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{
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return (unsigned long *)(__scs_base(tsk) + SCS_SIZE - sizeof(long));
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}
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static inline void scs_set_magic(struct task_struct *tsk)
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{
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*scs_magic(tsk) = SCS_END_MAGIC;
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}
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void scs_task_init(struct task_struct *tsk)
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{
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task_set_scs(tsk, NULL);
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}
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void scs_task_reset(struct task_struct *tsk)
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{
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task_set_scs(tsk, __scs_base(tsk));
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}
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void scs_set_init_magic(struct task_struct *tsk)
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{
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scs_save(tsk);
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scs_set_magic(tsk);
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scs_load(tsk);
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}
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static void scs_account(struct task_struct *tsk, int account)
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{
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mod_zone_page_state(page_zone(__scs_page(tsk)), NR_KERNEL_SCS_BYTES,
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account * SCS_SIZE);
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}
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int scs_prepare(struct task_struct *tsk, int node)
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{
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void *s;
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s = scs_alloc(node);
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if (!s)
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return -ENOMEM;
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task_set_scs(tsk, s);
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scs_set_magic(tsk);
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scs_account(tsk, 1);
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return 0;
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}
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#ifdef CONFIG_DEBUG_STACK_USAGE
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static inline unsigned long scs_used(struct task_struct *tsk)
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{
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unsigned long *p = __scs_base(tsk);
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unsigned long *end = scs_magic(tsk);
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uintptr_t s = (uintptr_t)p;
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while (p < end && *p)
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p++;
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return (uintptr_t)p - s;
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}
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static void scs_check_usage(struct task_struct *tsk)
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{
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static DEFINE_SPINLOCK(lock);
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static unsigned long highest;
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unsigned long used = scs_used(tsk);
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if (used <= highest)
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return;
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spin_lock(&lock);
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if (used > highest) {
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pr_info("%s: highest shadow stack usage %lu bytes\n",
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__func__, used);
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highest = used;
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}
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spin_unlock(&lock);
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}
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#else
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static inline void scs_check_usage(struct task_struct *tsk)
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{
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}
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#endif
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bool scs_corrupted(struct task_struct *tsk)
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{
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return *scs_magic(tsk) != SCS_END_MAGIC;
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}
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void scs_release(struct task_struct *tsk)
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{
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void *s;
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s = __scs_base(tsk);
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if (!s)
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return;
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BUG_ON(scs_corrupted(tsk));
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scs_check_usage(tsk);
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scs_account(tsk, -1);
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scs_task_init(tsk);
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scs_free(s);
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}
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